Methods of treating water to remove contaminants and water treatment plants for the practice thereof

ABSTRACT

The present disclosure relates to methods of treating water to remove contaminants, including harmful metal ions, and water treatment plants for practicing such methods. In an embodiment, the process includes adding a sulfur-containing, metal-decreasing agent; an iron (III)-containing, metalloid-decreasing agent; forming a solid precipitate from the contaminated water, wherein the solid precipitate includes a solid metal sulfide, a solid iron metalloid, a solid calcium metalloid, or a combination thereof; and separating the contaminated water from the solid precipitate to form purified water.

TECHNICAL FIELD

The present disclosure relates to methods of treating water to removecontaminants, including harmful metal ions, and water treatment plantsfor practicing such methods.

BACKGROUND

Clean water is essential for life. As earth's population increases toover 7.5 billion, the need for water to sustain human life, animal life,and agriculture increases. As industrialization increases, the demandfor clean water increases, and the pollution of clean water sourcesusually increases too.

Many methods have been developed to purify water by removing debris,salts, bacteria, harmful metal ions, harmful organic compounds, andmore. However, many of the methods of treating water are impractical forproviding large amounts of clean water. For example, distillation hashigh energy requirements. Similarly, evaporation requires tying up largevolumes for the duration of the evaporation process. Reverse osmosistypically provides very clean water, but is impractical for largevolumes of water and may not remove all harmful metal ions.

For example, in San Francisco the water usage per person ranges fromabout 130 to 232 gallons per day, and the population of San Francisco isover 800,000. Also, agriculture consumes from about 30 to about 50% ofthe water used in California.

Also, many of the water purification techniques discussed above purifymost of the water by concentrating all of the salts, metal ions, andmetalloids into a concentrated brine. All desalination plants regardlessof technology produce a concentrated brine that must be collected andremediated with the “reject” salts and solids properly disposed.Treating and disposing of concentrated brines is one of the mostpressing needs in the water industry today.

There is a dire need for a method of treating water that can removeharmful contaminants, especially harmful metal ions and metalloids fromwater. There is a need for a method of treating water that can be scaledup to process hundreds of gallons of water per minute. There is a needfor a method of treating water that has low energy requirements and usesinexpensive, readily available starting materials. There is a need forthe remediation of brines generated from desalination processes.

SUMMARY

The present disclosure relates to a method of treating contaminatedwater. In an embodiment, the method or process for treating contaminatedwater includes adding at least one sulfur-containing, metal-decreasingagent to the contaminated water; adding at least one iron(III)-containing, metalloid-decreasing agent or at least onecalcium-containing, metalloid-decreasing agent to the contaminatedwater; forming a solid precipitate from the contaminated water, whereinthe solid precipitate includes a solid metal sulfide, a solid ironmetalloid, a solid calcium metalloid, or a combination thereof; andseparating the contaminated water from the solid precipitate to formpurified water. In an embodiment, the process further comprises orincludes adding a hardness decreasing agent to the contaminated water,wherein the hardness decreasing agent includes a sulfate, a carbonate,or a combination thereof. In an embodiment, the process further includesadding a sulfate decreasing agent or a chloride decreasing agent to thecontaminated water, wherein at least one of the sulfate decreasing agentand the chloride decreasing agent include a barium containing compound,a bismuth containing compound, or a combination thereof. In anembodiment, the step of adding at least one iron (III)-containing,metalloid-decreasing agent to the contaminated water occurs during orafter the step of adding at least one sulfur-containing,metal-decreasing agent to the contaminated water. In an embodiment, atleast one sulfur-containing, metal-decreasing agent includes CH₄N₂S,C₂H₅NS, NaHS, KHS, H₂S, or a combination thereof. In an embodiment,wherein, provided that the contaminated water contains a metal ionselected from the group consisting of cadmium, chromium, copper, lead,mercury, zinc, nickel, any metal ion that forms a solid sulfideprecipitate, or a combination thereof, the solid metal sulfide isselected from the group consisting of a cadmium sulfide, a chromiumsulfide, a copper sulfide, a lead sulfide, a mercury sulfide, a zincsulfide, a nickel sulfide, any metal ion that forms a solid sulfideprecipitate, or a combination thereof. In an embodiment, the iron(III)-containing, metalloid-decreasing agent includes Fe₂(SO₄)₃, FeCl₃,ammonium iron(III) sulfate, or a combination thereof. In an embodiment,wherein, provided that the contaminated water contains a metalloidselected from the group consisting of an arsenate, a selenate, a borate,an antimonate, a phosphate, or a combination thereof, the solid ironmetalloid is selected from the group consisting of an iron arsenate, aniron selenite, an iron borate, an iron antimonate, an iron phosphate, aniron hydroxide, or a combination thereof. In an embodiment, wherein thehardness decreasing agent includes, but is not limited to, (NH₃)₂SO₄,(NH₃)₂CO₃, NH₃HCO₃, Na₂SO₄, Na₂CO₃, NaHCO₃, any metal ion that forms asolid sulfide precipitate, or a combination thereof. In an embodiment,provided that the contaminated water contains magnesium, calcium, or acombination thereof, the solid contaminant includes MgSO₄, MgCO₃, CaSO₄,CaCO₃, or a combination thereof. In an embodiment, the sulfate/chloridedecreasing agent contains Ba(NO₃)₂, BaCl₂, Bi(NO₃)₃, a bismuthoxynitrate (BiO(NO₃)), or a combination thereof. In an embodiment,provided that the contaminated water contains chloride, sulfate, or acombination thereof, the solid contaminant includes barium chloride,barium sulfate, bismuth oxychloride, bismuth sulfate, or a combinationthereof. In an embodiment, the purified water contains a fertilizerselected from the group consisting of NH₂CN, NaNO₃, KNO₃, NH₃NO₃, or acombination thereof. In an embodiment, the process further includes adesalinization step. In an embodiment, one or both of the at least onesulfur-containing, metal-decreasing agent or the at least one iron(III)-containing, metalloid-decreasing agent is added as a solid. In anembodiment, the process further includes measuring a level of metal ionor metalloid in the contaminated water.

In an embodiment, provided that the contaminated water contains borates,adding a series of reagents which increase the oxidation state of theborates to be precipitated with addition of calcium salts. The oxidantsinclude chemicals such as H₂O₂, Na₂O₂, CaO₂ or concentrated gaseousoxygen, and the calcium salts include Ca(OH)₂, CaO, CaCl₂. Theboron-containing precipitate includes calcium meta-borate and, calciumhydroborate. In some cases, this process may be performed after theother contaminants have been removed, as the procedure may solubilizesome of the precipitated contaminants.

A water treatment plant for performing the processes or methodsdescribed in the preceding paragraph is disclosed. In an embodiment, awater treatment plant for performing a process is disclosed, wherein theprocess includes treating contaminated water by one or more steps whichincludes adding at least one sulfur-containing, metal-decreasing agentto the contaminated water; adding at least one iron (III)-containing,metalloid-decreasing agent or at least one calcium-containing,metalloid-decreasing agent to the contaminated water; forming a solidprecipitate from the contaminated water, wherein the solid precipitateincludes a solid metal sulfide, a solid iron metalloid, a solid calciummetalloid, or a combination thereof; and separating the contaminatedwater from the solid precipitate to form purified water. In anembodiment, the water treatment plant can be configured to perform thefollowing steps, in order: adding at least one sulfur-containing,metal-decreasing agent to the contaminated water; adding at least oneiron (III)-containing, metalloid-decreasing agent or adding at least onecalcium-containing, metalloid-decreasing agent to the contaminatedwater; and adding a sulfate/chloride decreasing agent to thecontaminated water, wherein the sulfate decreasing agent includes abarium containing compound, a bismuth containing compound, or acombination thereof; and wherein the purified water contains afertilizer. In an embodiment, the water treatment plant includes a waterinlet; a water outlet; and one or more reaction vessels, wherein atleast one of the reaction vessels is connected to the water inlet and atleast one of the reaction vessels is connected to the water outlet,wherein the water treatment plant is configured to add at least onesulfur-containing, metal-decreasing agent or the at least one iron(III)-containing, metalloid-decreasing agent to at least one of thereaction vessels. In an embodiment, the water treatment plant is furtherconfigured to add a hardness decreasing agent to the contaminated water,wherein the hardness decreasing agent includes a sulfate, a carbonate,or a combination thereof.

A process for treating contaminated water and producing water containinga fertilizer is disclosed. In an embodiment, the process includes addingone or both of at least one sulfur-containing, metal-decreasing agent orat least one iron (III)-containing, metalloid-decreasing agent to thecontaminated water; forming a solid contaminant, wherein the solidcontaminant includes a solid metal sulfide, a solid iron metalloid, or acombination thereof; and removing the contaminated water from the solidcontaminant to form purified water, wherein the purified water containsa fertilizer. In an embodiment, the process further includes adding atleast one sulfur-containing, metal-decreasing agent or at least one iron(III)-containing, metalloid-decreasing agent into one, two or more tanksindividually, in sequence, or in a combination. In an embodiment, theprocess further includes transferring fluid from tank to tank, filteringafter each tank. In an embodiment, the process further includes removalof a solid precipitate before, after, or during any reagent additionsteps by filtering or settling. In an embodiment, the process furtherincludes collecting the solid contaminants generated. In an embodiment,the process further includes concentrating or drying the solidprecipitate before disposal.

A process for treating contaminated or ion-containing water isdisclosed. In an embodiment, the process includes adding at least onesulfur-containing, metal-decreasing agent, at least one iron(III)-containing, metalloid-decreasing agent, a hardness decreasingagent, at least one sulfate reducing agent, and adding a sulfatedecreasing agent, or any order or combination thereof, and removingion-contaminants identified or quantified from contaminated water.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe embodiments, will be better understood when read in conjunction withthe attached drawings. For the purpose of illustration, there are shownin the drawings some embodiments, which may be preferable. It should beunderstood that the embodiments depicted are not limited to the precisedetails shown, and are not drawn to scale.

FIG. 1 . An embodiment of the water treatment plant for performing anembodiment of the process is depicted in a flow chart.

FIG. 2 . An embodiment of the water treatment plant for performing anembodiment of the process is depicted in a flow chart.

DETAILED DESCRIPTION

Unless otherwise noted, all measurements are in standard American units,and standard metric units.

Unless otherwise noted, all instances of the words “a,” “an,” or “the”can refer to one or more than one of the word that they modify.

Unless otherwise noted, the phrase “at least one of” means one or morethan one of an object. For example, “at least one of” four tanks meansany one, two, three, or four tanks, or any combination thereof.

Unless otherwise noted, “contaminated water” means water that includesdissolved metal ions, metalloids, or a combination thereof. For example,the contaminated water can be a brine or brackish water that has beengenerated as a byproduct of a desalination process. Contaminated watercan come from any source.

It is understood that metals can be present in contaminated water as ametal or a metal ion. However, metals are typically heavy solids thatare easily filtered out. Therefore, unless otherwise noted, the term“metal” refers to a metal dissolved as a metal ion. For example, a“metal-reducing agent” refers to an agent capable of reducing the amountof metal ions present in the contaminated water. Similarly, the term“metal removal tank” refers to a vessel for removing metal ions.

A process for treating contaminated water is disclosed. In anembodiment, the method includes adding at least one sulfur-containing,metal-decreasing agent to the contaminated water. The at least onesulfur-containing, metal-decreasing agent is not generally limited solong as the at least one sulfur-containing, metal-decreasing agent iscapable of decreasing the amount or concentration of metal ions in thecontaminated water. In an embodiment, at least one sulfur-containing,metal-decreasing agent includes CH₄N₂S, C₂H₅NS, NaHS, KHS, H₂S, or acombination thereof. One benefit of the sulfur-containing,metal-decreasing agent can be that the addition of thesulfur-containing, metal-decreasing agent reduces the metal ions intometals that precipitate as a solid metal sulfide that can be easilyfiltered from the contaminated water. Another benefit of thesulfur-containing, metal-decreasing agent can be that the addition ofthe sulfur-containing, metal-decreasing agent reduces the positivecharge on a metal ion to a lower charge, which facilitates the reductionand/or removal of the metal ions in later steps. In an embodiment,provided that the contaminated water contains a metal ion selected fromthe group consisting of cadmium, chromium, copper, lead, mercury, zinc,nickel, any metal ion that forms a solid sulfide precipitate, or acombination thereof, then the solid metal sulfide can be selected fromthe group consisting of a cadmium sulfide, a chromium sulfide, a coppersulfide, a lead sulfide, a mercury sulfide, a zinc sulfide, a nickelsulfide, any metal ion that forms a solid sulfide precipitate, or acombination thereof, respectively. One benefit of reducing or decreasingamounts or concentrations of cadmium, chromium, copper, lead, mercury,zinc, and nickel is that many of these metal ions are toxic or limitedby regulation.

It is understood that adding at least one sulfur-containing,metal-decreasing agent to the contaminated water reduces or decreasesthe amount of metal ions on a stoichiometric basis. In an embodiment,the amount or concentration of metal ions is measured by techniquesknown in the art before or during the addition the sulfur-containing,metal-decreasing agent. For example, the sulfur-containing,metal-decreasing agent can be added during or after the amount orconcentration of metal ions is quantified by mass spec,electrochemistry, disposable strips, and the like. One benefit ofmeasuring the amount of metal ions present in the contaminated water caninclude saving costs by not adding excess sulfur-containing,metal-decreasing agent. One benefit of measuring the amount of metalions present in the contaminated water can include avoiding the furthercontamination of the water with a sulfur-containing, metal-decreasingagent.

In an embodiment, the at least one sulfur-containing, metal-decreasingagent can be added as a dry solid or dissolved in or carried by aliquid. One benefit to adding at least one sulfur-containing,metal-decreasing agent as a dry solid can be that the solid formfacilitates the precipitation of the metal sulfides formed. In anembodiment, the dry solid is added by a conveyor belt or other meteringconveyor. One benefit to adding a metal-decreasing agent as a liquid canbe the ability to easily spray the liquid across large areas of water.

In an embodiment, the method includes adding at least one iron(III)-containing, metalloid-decreasing agent or at least onecalcium-containing, metalloid-decreasing agent to the contaminatedwater. The iron (III)-containing, metalloid-decreasing agent is notgenerally limited so long as the iron (III)-containing,metalloid-decreasing agent is capable of decreasing the amount orconcentration of metalloids, such as an arsenate, a selenate/selenite, aborate, and/or a phosphate, many of which are toxic or limited byregulation. In an embodiment, the at least one iron (III)-containing,metalloid-decreasing agent includes Fe₂(SO₄)₃, FeCl₃, ammonium iron(III)sulfate, or a combination thereof. One benefit of adding the iron(III)-containing, metalloid-decreasing agent can be the formation orprecipitation of solid iron containing salts, which can be easilyfiltered from the contaminated water. Another benefit of adding at leastone iron (III)-containing, metalloid-decreasing agent during or after atleast one sulfur-containing, metal-decreasing agent can be furtherdecreasing the amount or concentration of metal ions that were notcompletely reduced to metal sulfide or precipitated by only the additionof the sulfur-containing, metal-decreasing agent. In an embodiment,provided that the contaminated water contains a metalloid selected fromthe group consisting of an arsenate, a selenate/selenite, a borate, aphosphate, or a combination thereof, then the solid iron metalloidformed would be an iron arsenate, an iron selenate or iron selenite, aniron borate, an iron phosphate, an iron hydroxide, or a combinationthereof, respectively.

It is understood that adding at least one iron (III)-containing,metalloid-decreasing agent or at least one calcium-containing,metalloid-decreasing agent to the contaminated water reduces ordecreases the amount of metalloid compounds or metal ions on astoichiometric basis. In an embodiment, the amount or concentration ofmetalloids can be measured by techniques known in the art before orduring the addition the iron (III)-containing, metalloid-decreasingagent or the calcium-containing, metalloid-decreasing agent. Forexample, the addition of the iron (III)-containing, metalloid-decreasingagent or calcium-containing, metalloid-decreasing agent can be addedduring or after the amount or concentration of metalloids is quantifiedby mass spectroscopy, electrochemistry, disposable strips, and the like.One benefit of measuring the amount of metalloids present in thecontaminated water can be avoiding the addition of excess iron(III)-containing, metalloid-decreasing agent or at least onecalcium-containing, metalloid-decreasing agent, which can save on thecosts of these materials. One benefit of measuring the amount ofmetalloids present in the contaminated water can be avoiding furthercontamination of the water with excess iron (III)-containing,metalloid-decreasing agent or calcium-containing, metalloid-decreasingagent.

In an embodiment, at least one iron (III)-containing,metalloid-decreasing agent or at least one calcium-containing,metalloid-decreasing agent can be added as a dry solid or dissolved in aliquid. One benefit to adding at least one iron (III)-containing,metalloid-decreasing agent or at least one calcium-containing,metalloid-decreasing agent as a dry solid can be that the solid formfacilitates the precipitation of the iron (III) or calcium metalloidformed. In an embodiment, the dry solid is added by a convey belt. Onebenefit to adding at least one iron (III)-containing,metalloid-decreasing agent or at least one calcium-containing,metalloid-decreasing agent as a liquid can be the ability to easilyspray the liquid across large areas of contaminated water.

In an embodiment, the process disclosed herein includes treatingcontaminated water by adding at least one sulfur-containing,metal-decreasing agent to the contaminated water, and adding at leastone iron (III)-containing, metalloid-decreasing agent, or at least onecalcium-containing, metalloid-decreasing agent to the contaminatedwater. While these steps separately may have been performed to purifywater in the past, it has been found that the combination of these stepsprovides a benefit of removing all or substantially all toxic metal ionsand metalloids from the contaminated water. Further, this combinationcan treat vast volumes of contaminated water without high energyrequirements because the toxic contaminants are precipitated out ofsolution as solids that can be easily separated from the water by highvolume techniques such as filtration, decantation, settling, and thelike, yielding water with reduced harmful contaminants. One reason thatno one appears to have combined these steps before is that it could beseen as the addition of one set of contaminates to remove another set ofcontaminates. However, one benefit of the present method can be thatboth steps add stoichiometric amounts of sulfur-containing,metal-decreasing agent and iron (III)-containing, metalloid-decreasingagent, and/or at least one calcium-containing, metalloid-decreasingagent such that these additives reduce, decrease, or eliminate toxiccontaminates present in the contaminated water. Also, if there is aslight excess of these additives in the water they can be removed bylater steps. If there is a slight excess of these additives in the waterthese additives would likely be less toxic than the metal ions andmetalloids removed. For example, any residual sulfate would be expectedto be less toxic for many uses than arsenate or cadmium ions.

In an embodiment, the process disclosed above can further include addinga hardness decreasing agent to the contaminated water, wherein thehardness decreasing agent includes a sulfate, a carbonate, or acombination thereof. In an embodiment, the hardness decreasing agentincludes (NH₃)₂SO₄, (NH₃)₂CO₃, NH₃HCO₃, Na₂SO₄, Na₂CO₃, NaHCO₃, anymetal carbonate or sulfate that forms a metal sulfide precipitate, or acombination thereof. In an embodiment, provided that the contaminatedwater contains magnesium, calcium, or a combination thereof, then asolid precipitate or solid contaminate will be formed which includesMgSO₄, MgCO₃, CaSO₄, CaCO₃, or a combination thereof.

In an embodiment, the step of adding a hardness decreasing agent to thecontaminated water is optional, because the removal of calcium ions andmagnesium ions is not important for many applications of water. However,one benefit of removing calcium ions and magnesium ions can bepreventing or decreasing the occurrence of unintentional mineraldeposits, such as calcium deposits, which can clog pipes, sprayers, andother water tools. In an embodiment, the step of adding a hardnessdecreasing agent to the contaminated water provides a benefit ofremoving sulfate ions added in, for example, the metalloid decreasingstep. In this embodiment, there is a sort of ion exchange that can bethought of as replacing calcium ions, magnesium ions, carbonates, and/orsulfates with ammonium ions, sodium ions, and nitrate ions.

It has been found that one of the challenges of adding chemicals toremove chemicals is that it can be difficult to remove all chemicalsbecause they do not completely remove each other. Therefore, in anembodiment of the process, there is a synergy among the steps where theaddition of ammonium ions, sodium ions, and nitrate ions to remove moreother chemicals results in purified water containing an amount of NH₂CN,NaNO₃, KNO₃, NH₃NO₃, and combinations thereof, which are known to besafe fertilizers. For many uses, such as agriculture, people pay to addthese fertilizers to clean water before spraying the water onto fields.In an embodiment, the present method generates purified water thatcontains a fertilizer, including NH₂CN, NaNO₃, KNO₃, NH₃NO₃, andcombinations thereof, as a valuable byproduct.

In an embodiment, the process includes a step of adding a sulfatedecreasing agent or a chloride decreasing agent to the contaminatedwater. In an embodiment, this step is optional because some embodimentsadd a hardness reducing agent, which also removes sulfate. In anembodiment, this step is optional because low levels of chloride aregenerally safe in water for human consumption and agricultural use. Inan embodiment, one benefit to removing chloride from water can be theprevention or reduction of corrosion in pipes. In an embodiment, thesulfate decreasing agent and/or the chloride decreasing agent include abarium containing compound, a bismuth containing compound, or acombination thereof. Suitable sulfate decreasing agents or chloridedecreasing agents include Ba(NO₃)₂, BaCl₂, Bi(NO₃)₃, a bismuthoxynitrate, or a combination thereof. In an embodiment, provided thatthe contaminated water contains chloride, sulfate, or a combinationthereof, then a solid precipitate or solid contaminant can be formedthat includes barium chloride, barium sulfate, bismuth oxychloride,bismuth sulfate, or a combination thereof. In an embodiment of theprocess, the solid precipitate can be removed from the contaminatedwater during or after the addition of a sulfate decreasing agent or achloride decreasing agent to the contaminated water. In an embodiment,the solid precipitate can be removed by any method of removing a liquidfrom a solid including filtering, settlement, and the like.

In an embodiment, the process includes measuring or quantifying a levelof metalloid, metal ion, or other contaminant in the water before,during, or after any step of the process, including any addition step.One benefit of performing a measuring or quantifying step before orduring an addition step can be determining how much reactant to addduring the addition step. One benefit to performing a measuring orquantifying step during or after each step can be to ensure that nocontaminants accidently slip through the process. In an embodiment, thecontaminated water or purified water from any step of the process can berecycled to any other step of the process for further processing.

In an embodiment, the process includes a further step of desalinationbefore any other step. In an embodiment, the process does not includedesalination, and the process can be performed on a brine water obtainedfrom a desalination process. One benefit to treating brine water fromany source is that contaminates are more concentrated, which leads tomore efficient treatment or remediation of the contaminated water pervolume processed. In an embodiment, any of the solid precipitategenerated by the process or water treatment plant can be collected,dried, concentrated, or otherwise processed to recover valuablematerials or make the precipitate safer for proper disposal.

In an embodiment, a process includes a step of measuring an amount ofmetal ions in the contaminated water, measuring the absence orsubstantial absence of metal ions, and excluding the addition of atleast one sulfur-containing, metal-decreasing agent to the contaminatedwater such that the process further includes adding at least one iron(III)-containing, metalloid-decreasing agent or at least onecalcium-containing, metalloid-decreasing agent to the contaminatedwater; forming a solid precipitate from the contaminated water, whereinthe solid precipitate includes a solid metal sulfide, a solid ironmetalloid, a solid calcium metalloid, or a combination thereof; andseparating the contaminated water from the solid precipitate to formpurified water.

A water treatment plant or facility is disclosed. In an embodiment, thewater treatment plant can include one reaction vessel; or two or morereaction vessels, the two or more of the reaction vessels beinginterconnected. In an embodiment, the water treatment plant includes 1,2, 3, 4, or 5 reaction vessels. Referring to FIG. 1 , in an embodiment,the water treatment plant 100 can be configured to start with a brackishwater inlet 142, which may include water from any source. In anembodiment, the water treatment plant can be configured to treatbrackish water by a desalination process 102, which separates the impurewater into clean fresh water 144 and a brine or contaminated water 132.In another embodiment, the water treatment plant does not include adesalination process and starts with a brine or contaminated water 132.In an embodiment, the water treatment plant is connected in line with adesalination plant.

In an embodiment, the water treatment plant can be configured to pumpcontaminated water into a first reaction vessel 104 or first tank. In anembodiment, the water treatment plant can be configured to add at leastone sulfur-containing, metal-decreasing agent 114, which includesCH₄N₂S, C₂H₅NS, NaHS, KHS, H₂S, or a combination thereof, to thecontaminated water to form a first solid precipitate 124, which caninclude metal sulfides. In an embodiment, the water treatment plant canbe configured to pump the water through a first filter 134 to remove thefirst solid precipitate as the contaminated water is pumped or passedinto the second reaction vessel 106. In another embodiment, the metalsulfide precipitates are not removed from the contaminated water andflow in the solution to be used as precipitate seeds for further stages.In an embodiment, the interim filter 134 is optional.

In an embodiment, the plant is configured to add at least one iron(III)-containing, metalloid-decreasing agent and/or add at least onecalcium-containing, metalloid-decreasing agent 116, which includesFe₂(SO₄)3, FeCl₃, ammonium iron(III) sulfate, or a combination thereof,to the contaminated water to form a second solid precipitate 126, whichincludes solid iron metalloids. In an embodiment, the water treatmentplant can be configured to pump the water through a second filter 136 toremove the second solid precipitate as the contaminated water is pumpedor passed into a third reaction vessel 108. In another embodiment, theiron (III) metalloid precipitates are not removed from the contaminatedwater and flow in the solution to be used as precipitate seeds forfurther stages. In an embodiment, the interim filter 136 is optional. Inan embodiment, the water treatment plant can be configured to add ahardness decreasing agent 118 to the contaminated water, wherein thehardness decreasing agent includes a sulfate, a carbonate, or acombination thereof, to form a third solid precipitate 128, whichincludes MgSO₄, MgCO₃, CaSO₄, CaCO₃, or a combination thereof. In anembodiment, the water treatment plant can be configured to pump thecontaminated water through a third filter 138 into a fourth reactionvessel 110. In another embodiment, the hardness-reducing precipitatesare not removed from the contaminated water and flow in the solution tobe used as precipitate seeds for further stages. In an embodiment, theinterim filter 138 is optional. In an embodiment, the water treatmentplant can be configured to add a sulfate decreasing agent 120 or achloride decreasing agent to the contaminated water, wherein at leastone of the sulfate decreasing agent and the chloride decreasing agentinclude a barium containing compound, a bismuth containing compound, ora combination thereof, to form a fourth solid precipitate 130, whichincludes barium chloride, barium sulfate, bismuth oxychloride, bismuthsulfate, or a combination thereof.

In an embodiment, the water treatment plant can be configured to removethe fourth precipitate by filtration through a fourth filter 140 toprovide a purified water 146, wherein the purified water may contain afertilizer, including NH₂CN, NaNO₃, KNO₃, NH₃NO₃, or a combinationthereof. In another embodiment, only one filter is used at the end ofthe treatment process to remove all of the precipitates from thecontaminated water. In an embodiment, final filter 140 is not optional.

In an embodiment, as depicted in FIG. 1 , the water treatment plant canbe configured to perform the following steps, in order: adding at leastone sulfur-containing, metal-decreasing agent to the contaminated water;adding at least one iron (III)-containing, metalloid-decreasing agent oradding at least one calcium-containing, metalloid-decreasing agent tothe contaminated water; and adding a sulfate decreasing agent to thecontaminated water, wherein the sulfate decreasing agent includes abarium containing compound, a bismuth containing compound, or acombination thereof; and forming a purified water containing afertilizer.

In an embodiment, the water treatment plant can be configured to includeany number of filters to remove solid precipitates, including 1, 2, 3,or 4 filters, because the filters are optional. In an embodiment, anyreaction vessel can be connected or disconnected from any other reactionvessel. In an embodiment, the water treatment plant can perform 1, 2, 3,or 4 of the steps using only 1, 2, or 3 reaction vessels. In anembodiment, the water treatment plant is configured to perform all ofthe reaction steps in a single reaction vessel by adding the eachreactant in any sequence or simultaneously. However, it has been foundthe highest treatment efficiency can be provided by adding each reactantto a separate reaction vessel to form a precipitate that is filtered outafter the last step. Referring to FIG. 2 , in an embodiment, a watertreatment plant 200 is identical to that of FIG. 1 , except that thewater treatment plant 200 is configured to have only one filter orsettling pond 140, which removes all of the precipitates 124, 126, 128,and 130 to provide purified water 146. One benefit of this configurationcan be that the precipitates are swept from one reaction vessel to thenext reaction vessel, such that the presence of a solid facilitates theformation of the next precipitate to be formed. In this embodiment, theprecipitates are removed in the same step.

In Several Exemplary Embodiments

Embodiment 1. A process for treating contaminated water comprising:

adding at least one sulfur-containing, metal-decreasing agent to thecontaminated water;

adding at least one iron (III)-containing, metalloid-decreasing agent orat least one calcium-containing, metalloid-decreasing agent to thecontaminated water;

forming a solid precipitate from the contaminated water, wherein thesolid precipitate includes a solid metal sulfide, a solid ironmetalloid, a solid calcium metalloid, or a combination thereof; and

separating the contaminated water from the solid precipitate to formpurified water.

Embodiment 2. The process of any of embodiments 1 or 3-15, furthercomprising:

adding a hardness decreasing agent to the contaminated water, whereinthe hardness decreasing agent includes a sulfate, a carbonate, or acombination thereof.

Embodiment 3. The process of any of embodiments 1-2 or 4-15, furthercomprising:

adding a sulfate decreasing agent or a chloride decreasing agent to thecontaminated water, wherein at least one of the sulfate decreasing agentand the chloride decreasing agent include a barium containing compound,a bismuth containing compound, or a combination thereof.

Embodiment 4. The process of any of embodiments 1-3 or 5-15, whereinadding at least one iron (III)-containing, metalloid-decreasing agent tothe contaminated water occurs during or after adding at least onesulfur-containing, metal-decreasing agent to the contaminated water.

Embodiment 5. The process of any of embodiments 1-4 or 6-15, wherein theat least one sulfur-containing, metal-decreasing agent includes CH₄N₂S,C₂H₅NS, NaHS, KHS, H₂S, or a combination thereof.

Embodiment 6. The process of any of embodiments 1-5 or 7-15, wherein,provided that the contaminated water contains a metal ion selected fromthe group consisting of cadmium, chromium, copper, lead, mercury, zinc,nickel, any metal ion that forms a solid sulfide precipitate, or acombination thereof,

the solid metal sulfide is selected from the group consisting of acadmium sulfide, a chromium sulfide, a copper sulfide, a lead sulfide, amercury sulfide, a zinc sulfide, a nickel sulfide, any metal that formsa solid sulfide precipitate, or a combination thereof.

Embodiment 7. The process of any of embodiments 1-6 or 8-15, wherein theiron (III)-containing, metalloid-decreasing agent includes Fe₂(SO₄)₃,FeCl₃, ammonium iron(III) sulfate, or a combination thereof.

Embodiment 8. The process of any of embodiments 1-7 or 9-15, wherein,provided that the contaminated water contains a metalloid selected fromthe group consisting of an arsenate, a selenate or a selenite, a borate,a phosphate, or a combination thereof,

the solid iron metalloid is selected from the group consisting of aniron arsenate, an iron selenite, an iron borate, a metaborate, an ironphosphate, an iron hydroxide, or a combination thereof.

Embodiment 9. The process of any of embodiments 1-8 or 10-15, whereinthe hardness decreasing agent includes (NH₃)₂SO₄, (NH₃)₂CO₃, NH₃HCO₃,Na₂SO₄, Na₂CO₃, NaHCO₃, any metal that forms a solid sulfideprecipitate, or a combination thereof; and

wherein, provided that the contaminated water contains magnesium,calcium, or a combination thereof, the solid precipitate includes MgSO₄,MgCO₃, CaSO₄, CaCO₃, or a combination thereof.

Embodiment 10. The process of any of embodiments 1-9 or 11-15, whereinthe sulfate decreasing agent contains Ba(NO₃)₂, BaCl₂, Bi(NO₃)₃, abismuth oxynitrate, or a combination thereof.

Embodiment 11. The process of any of embodiments 1-10 or 12-15, wherein,provided that the contaminated water contains chloride, sulfate, or acombination thereof, the solid precipitate includes barium chloride,barium sulfate, bismuth oxychloride, bismuth sulfate, or a combinationthereof.

Embodiment 12. The process of any of embodiments 1-11 or 13-15, whereinthe purified water contains a fertilizer selected from the groupconsisting of NH₂CN, NaNO₃, KNO₃, NH₃NO₃, or a combination thereof.

Embodiment 13. The process of any of embodiments 1-12 or 14-15, furthercomprising a desalinization step.

Embodiment 14. The process of any of embodiments 1-13 or 15, wherein oneor both of the at least one sulfur-containing, metal-decreasing agent orthe at least one iron (III)-containing, metalloid-decreasing agent isadded as a solid.

Embodiment 15. The process of any of embodiments 1-14, furthercomprising:

measuring a level of metal ion or metalloid in the contaminated water.

Embodiment 16. A water treatment plant configured to perform the processof any of embodiments 1-15 comprising:

one reaction vessel; or two or more reaction vessels, the two or more ofthe reaction vessels being interconnected.

Embodiment 17. The water treatment plant of any of embodiments 16 or18-19, configured to perform the following steps, in order:

adding at least one sulfur-containing, metal-decreasing agent to thecontaminated water;

adding at least one iron (III)-containing, metalloid-decreasing agent oradding at least one calcium-containing, metalloid-decreasing agent tothe contaminated water; and

adding a sulfate decreasing agent to the contaminated water, wherein thesulfate decreasing agent includes a barium containing compound, abismuth containing compound, or a combination thereof; and

providing a purified water containing a fertilizer.

Embodiment 18. The water treatment plant of any of embodiments 16-17 or19 comprising:

a water inlet;

a water outlet; and

one or more reaction vessels, wherein at least one of the reactionvessels is connected to the water inlet and at least one of the reactionvessels is connected to the water outlet,

wherein the water treatment plant is configured to add the at least onesulfur-containing, metal-decreasing agent or the at least one iron(III)-containing, metalloid-decreasing agent to at least one of thereaction vessels.

Embodiment 19. The water treatment plant of any of embodiments 16-18,wherein the water treatment plant is configured to add a hardnessdecreasing agent to the contaminated water, wherein the hardnessdecreasing agent includes a sulfate, a carbonate, or a combinationthereof.

Embodiment 20. A process for treating contaminated water comprising:

adding one or both of at least one sulfur-containing, metal-decreasingagent or at least one iron (III)-containing, metalloid-decreasing agentto the contaminated water;

forming a solid precipitate, wherein the solid precipitate includes asolid metal sulfide, a solid iron metalloid, or a combination thereof;and

removing the contaminated water from the solid precipitate to formpurified water, wherein the purified water contains a fertilizer.

Embodiment 21. A process for treating contaminated or ion-containingwater comprising:

adding at least one sulfur-containing, metal-decreasing agent, at leastone iron (III)-containing, metalloid-decreasing agent, a hardnessdecreasing agent, at least one sulfate reducing agent, and adding asulfate decreasing agent, or a combination thereof, simultaneously or inany order,

removing ion-contaminants identified or quantified from the contaminatedwater.

Embodiment 22. The process embodiment of 20, further comprising:

adding at least one sulfur-containing, metal-decreasing agent or atleast one iron (III)-containing, metalloid-decreasing agent into one,two or more tanks individually, in sequence, or in a combination.

Embodiment 23. The process embodiment of any of embodiments 21 or 22,further comprising:

transferring fluid from tank to tank, filtering after each tank.

Embodiment 24. The process of any of embodiments 21-23 or 25-26, furthercomprising:

removing of a solid precipitate before, after, or during any reagentaddition steps by filtering or settling.

Embodiment 25. The process of any of embodiments 21-24 or 26, furthercomprising:

collecting the solid precipitate.

Embodiment 26. The process of any of embodiments 21-25, furthercomprising:

concentrating or drying the solid precipitate before disposal.

EXAMPLES Example 1

A water treatment plant was configured according to the design shown inFIG. 1 , as follows: The contaminated water flow rate and contaminantconcentrations was used to determine the different tank capacities thatwill be required for each stage of the process. For example, the plantwas sized for treating a certain flowrate of contaminated water. Totreat 500 gallons per minute (“gpm” or 1,892 liters per minute “LPM”) ofa contaminated solution, each tank should be capable of holdingsufficient solution for a mean estimated residence time determined byhow much contaminant must be removed from the water. To determine this,analytical information on the concentration of all of the genericspecies in the water (total metal ions, total metalloids, totalhardness, chloride and sulfate) was determined for an average sample ofthe water. The water contains 20,000 ppm total dissolved solids (TDS),with most of that chlorides, sulfates and calcium, with undetectablelevels of metal ions, and amounts of metalloids above the environmentallimits (typically 10 ppm), therefore the plant capable of treating thiswater had the following tank sizes, referring to FIG. 1 :

Metal removal tank 104 (not installed or installed but not used due tolack of metal ions as contaminants).

Metalloid removal tank 106 having an approximately 15,000 gallon (56,781L) capacity provided 30 minutes of residence time at an average inletflowrate of 500 gpm (1,892 LPM).

Hardness removal tank 108 having an approximately 15,000 gallon (56,781L) capacity provided 30 minutes of residence time at an average inletflowrate of 500 gpm (1,892 LPM).

Chloride and sulfate reducing tank 110 having an approximately 20,000gallon (75,708 L) capacity provided 40 minutes of residence time at anaverage inlet flowrate of 500 gpm (1,892 LPM).

Settling pond (thickener) for initial recovery of “treated” water (45′diameter thickener to allow hours of settling/decantation to the slurry.

Filter press 140 with over 100 ft² of available surface area fortreating the slurry from the thickener to recover the rest of the waterfrom the process

The reagent scheme that was used for this process was to add a smallamount of thiourea (SC(NH₂)₂) to the metalloid removal tank with smallamounts of calcium oxide (between 0.1 and 1 g/L) and iron(III) sulfate(between 1 and 5 g/L). The exact dosage of each reagent was determinedfrom the analyses of the initial water. Ferric sulfate (Fe₂(SO₄)₃) wasadded to complete the precipitation of iron (III)-selenite, iron(III)-calcium borate, iron (III)-arsenate and iron (III)-hydroxide. Thelatter can be a beneficial product from adding more than thestoichiometric amount of iron (III) than was needed for the full removalof the selenium and boron from the water. The precipitates were notfiltered prior to feeding the hardness removal tank so that the ironprecipitates were present to seed the precipitation of the hardnessreduction process.

Ammonium sulfate was added in the hardness removal tank to a levelcommensurate to the hardness of the solution. For this water, from 1-10g/L was maintained to ensure that the majority of the calcium andmagnesium was precipitated and replaced with ammonium ions. The calciumand magnesium sulfate precipitates grew on the existing precipitatesfrom the metalloid removal process.

The solution with all of the precipitates were then allowed to flow intothe last vessel (the chloride/sulfate reduction tank). A combination ofbarium nitrate and bismuth nitrate was added to reduce the chloride andthe sulfate concentrations in the water, and it was replaced with thenitrates from the added reagents. The barium sulfate and bismuthoxychloride precipitates were collected in the bulk precipitates nowformed in the vessel.

The final solution containing the precipitates was then fed to athickener. The 45-ft diameter was determined to provide sufficient timefor the precipitate to fully settle to the bottom of the thickener,where slow-moving rakes on the bottom gently move the settled materialto the center of the cone-shaped bottom for discharge. The thickenedprecipitate slurry was then pumped to a filter press, to separate theprecipitates from the water. Periodically, the filter press was openedto harvest the filtered solids for disposal.

This plant was capable of processing 500 gpm (1,892 LPM) of contaminatedwater, which is equivalent to remediating the brine output of a 5,000gpm (7.2 million gallons per day, 27,254,964 L per day) desalinationplant.

Example 2

Example 2 is identical to the process and water treatment plant inExample 1, except that metal ions are detected in the contaminatedwater, and metal removal tank 104 is installed and an equivalent orslight excess of amount of NaHS is added to the metal removal tank toprecipitate the metal ions detected.

What is claimed is:
 1. A process for treating contaminated watercomprising: adding at least one sulfur-containing, metal-decreasingagent to the contaminated water; adding at least one iron(III)-containing, metalloid-decreasing agent or at least onecalcium-containing, metalloid-decreasing agent to the contaminatedwater; forming a solid precipitate from the contaminated water, whereinthe solid precipitate includes a solid metal sulfide, a solid ironmetalloid, a solid calcium metalloid, or a combination thereof; andseparating the contaminated water from the solid precipitate to formpurified water.
 2. The process of claim 1, further comprising: adding ahardness decreasing agent to the contaminated water, wherein thehardness decreasing agent includes a sulfate, a carbonate, or acombination thereof.
 3. The process of claim 1, further comprising:adding a sulfate decreasing agent or a chloride decreasing agent to thecontaminated water, wherein at least one of the sulfate decreasing agentand the chloride decreasing agent include a barium containing compound,a bismuth containing compound, or a combination thereof.
 4. The processof claim 1, wherein adding at least one iron (III)-containing,metalloid-decreasing agent to the contaminated water occurs during orafter adding at least one sulfur-containing, metal-decreasing agent tothe contaminated water.
 5. The process of claim 1, wherein the at leastone sulfur-containing, metal-decreasing agent includes CH₄N₂S, C₂H₅NS,NaHS, KHS, H₂S, or a combination thereof.
 6. The process of claim 1,wherein, provided that the contaminated water contains a metal ionselected from the group consisting of cadmium, chromium, copper, lead,mercury, zinc, nickel, any metal ion that forms a solid sulfideprecipitate, or a combination thereof, the solid metal sulfide isselected from the group consisting of a cadmium sulfide, a chromiumsulfide, a copper sulfide, a lead sulfide, a mercury sulfide, a zincsulfide, a nickel sulfide, any metal that forms a solid sulfideprecipitate, or a combination thereof.
 7. The process of claim 1,wherein the iron (III)-containing, metalloid-decreasing agent includesFe₂(SO₄)₃, FeCl₃, ammonium iron(III) sulfate, or a combination thereof.8. The process of claim 1, wherein, provided that the contaminated watercontains a metalloid selected from the group consisting of an arsenate,a selenate or a selenite, a borate, a phosphate, or a combinationthereof, the solid iron metalloid is selected from the group consistingof an iron arsenate, an iron selenite, an iron borate, a metaborate, aniron phosphate, an iron hydroxide, or a combination thereof.
 9. Theprocess of claim 2, wherein the hardness decreasing agent includes(NH₃)₂SO₄, (NH₃)₂CO₃, NH₃HCO₃, Na₂SO₄, Na₂CO₃, NaHCO₃, any metal thatforms a solid sulfide precipitate, or a combination thereof; andwherein, provided that the contaminated water contains magnesium,calcium, or a combination thereof, the solid precipitate includes MgSO₄,MgCO₃, CaSO₄, CaCO₃, or a combination thereof.
 10. The process of claim3, wherein the sulfate decreasing agent contains Ba(NO₃)₂, BaCl₂,Bi(NO₃)₃, a bismuth oxynitrate, or a combination thereof.
 11. Theprocess of claim 3, wherein, provided that the contaminated watercontains chloride, sulfate, or a combination thereof, the solidprecipitate includes barium chloride, barium sulfate, bismuthoxychloride, bismuth sulfate, or a combination thereof.
 12. The processof claim 1, wherein the purified water contains a fertilizer selectedfrom the group consisting of NH₂CN, NaNO₃, KNO₃, NH₃NO₃, or acombination thereof.
 13. The process of claim 1, further comprising adesalinization step.
 14. The process of claim 1, wherein one or both ofthe at least one sulfur-containing, metal-decreasing agent or the atleast one iron (III)-containing, metalloid-decreasing agent is added asa solid.
 15. The process of claim 1, further comprising: measuring alevel of metal ion or metalloid in the contaminated water.
 16. A watertreatment plant configured to perform the process of claim 1 comprising:one reaction vessel; or two or more reaction vessels, the two or more ofthe reaction vessels being interconnected.
 17. The water treatment plantof claim 16, configured to perform the following steps, in order: addingat least one sulfur-containing, metal-decreasing agent to thecontaminated water; adding at least one iron (III)-containing,metalloid-decreasing agent or adding at least one calcium-containing,metalloid-decreasing agent to the contaminated water; and adding asulfate decreasing agent to the contaminated water, wherein the sulfatedecreasing agent includes a barium containing compound, a bismuthcontaining compound, or a combination thereof; and providing a purifiedwater containing a fertilizer.
 18. The water treatment plant of claim 16comprising: a water inlet; a water outlet; and one or more reactionvessels, wherein at least one of the reaction vessels is connected tothe water inlet and at least one of the reaction vessels is connected tothe water outlet, wherein the water treatment plant is configured to addthe at least one sulfur-containing, metal-decreasing agent or the atleast one iron (III)-containing, metalloid-decreasing agent to at leastone of the reaction vessels.
 19. The water treatment plant of claim 18,wherein the water treatment plant is configured to add a hardnessdecreasing agent to the contaminated water, wherein the hardnessdecreasing agent includes a sulfate, a carbonate, or a combinationthereof.
 20. A process for treating contaminated water comprising:adding one or both of at least one sulfur-containing, metal-decreasingagent or at least one iron (III)-containing, metalloid-decreasing agentto the contaminated water; forming a solid precipitate, wherein thesolid precipitate includes a solid metal sulfide, a solid ironmetalloid, or a combination thereof; and removing the contaminated waterfrom the solid precipitate to form purified water, wherein the purifiedwater contains a fertilizer.
 21. A process for treating contaminated orion-containing water comprising: adding at least one sulfur-containing,metal-decreasing agent, at least one iron (III)-containing,metalloid-decreasing agent, a hardness decreasing agent, at least onesulfate reducing agent, and adding a sulfate decreasing agent, or acombination thereof, simultaneously or in any order, removingion-contaminants identified or quantified from the contaminated water.22. The process claim of 20, further comprising: adding at least onesulfur-containing, metal-decreasing agent or at least one iron(III)-containing, metalloid-decreasing agent into one, two or more tanksindividually, in sequence, or in a combination.
 23. The process claim of21, further comprising: transferring fluid from tank to tank, filteringafter each tank.
 24. The process claim of 23, further comprising:removing of a solid precipitate before, after, or during any reagentaddition steps by filtering or settling.
 25. The process of claim 23,further comprising: collecting the solid precipitate.
 26. The process ofclaim 23, further comprising: concentrating or drying the solidprecipitate before disposal.